Great Balls o' Bryozoans

Thursday, August 01, 1996
The British Antarctic Survey vessel R.R.S. Bransfield was anchored off an 800-foot-thick frozen slab called the Brunt ice shelf when two passengers noticed some odd brown ball-like creatures floating by. They fished out three of the balls, hollow spheres .2 to .9 inch across, which turned out to consist of a thin layer of invertebrates called bryozoans, animals that normally live attached to the seafloor. Marine biologist Peter Hayward of the University of Wales and his colleagues speculate that the spherical colonies may be a juvenile form of a familiar bryozoan species. Perhaps, says Hayward, bryozoan larvae feed on algae that grow on the underside of sea ice; then they might accidentally surface when the ice breaks up in summer, before sinking to the bottom for good. But why they surface so rarely--and in spheres--is unknown. Forty years ago, says Hayward, a famous British marine biologist, Alistair Hardy, reported seeing similar balls and guessed their identity, but there haven’t been any confirmed captures of the spheres. Hardy said, ‘I saw some round balls in Antarctica, you know, bloody bryozoans!’ says Hayward. And that’s the only other account we know of.
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